In recent years, hard disk drives (commonly referred to as “HDD”) have been incorporated into household appliances such as personal video recorders (commonly referred to as “PVR's”). A hard disk drive in a typical PVR has enough memory capacity for several hundred hours of digital recording. Such high memory capacity is due to very high memory density, which has become possible by advancements in manufacturing. Due to the high density of memory cells, complex data reading and data writing techniques are required for the proper handling of data obtained from and written onto a hard disk drive in, for example, a PVR. The quality of the hard disk drive directly effects whether such complex data reading and data writing techniques may be practiced properly. This in turn affects the reliability of, and the noise generated from, the hard disk drive. The reliability of, and the noise generated from, the hard disk drive are factors that make modern PVRs attractive to consumers.
A typical hard disk drive includes a spindle motor. The spindle motor includes, for example, a fluid dynamic pressure bearing device. The fluid dynamic pressure bearing device includes a shaft, a sleeve that receives the shaft, and a layer of dynamic pressure fluid such as oil that resides between the shaft and the sleeve.
To attain optimum performance of the fluid dynamic pressure device, the fluid dynamic pressure of the dynamic pressure fluid should be maximized. In order to maximize the fluid dynamic pressure of the dynamic pressure fluid in the fluid dynamic pressure bearing device, it is necessary to prevent wet diffusion of the dynamic pressure fluid.
Wet diffusion may occur due to:
(A) the capillary action of the dynamic pressure fluid between the outer surface of the shaft and the inner surface of the sleeve;
(B) the scattering of the dynamic pressure fluid when, for example, the bearing device is started, stopped, accelerated, or subjected to an impact; and/or
(C) the possible overflow of the dynamic pressure fluid when the temperature of the bearing device has risen.
To prevent wet diffusion, it is known to form an oil repelling film on certain portions of the pressure bearing device and/or the hard disk drive. To form the oil repelling film, an oil repelling agent is first applied to a desired area and baked to form an oil repelling film.
To ensure the quality of the oil repelling film, the quality of the coating of the oil repelling agent and/or the quality of the oil repelling film itself must be inspected. One known inspection method is visual inspection.
A known oil repelling agent is a colorless and transparent resin of the fluorine system. An oil repelling film formed from such a resin is difficult to inspect by the naked eye. As a result, it is difficult to control the quality of the oil repelling film on a dynamic pressure bearing device, such as a fluid dynamic pressure bearing device. In the absence of visual inspection, the reliability of a spindle motor having an oil repelling film formed from such an oil repelling agent may be compromised due to wet diffusion.
The Official Publication of Toku Kai 2001-27242 proposed a solution to improve the visual examination of the quality of the coating of the oil repelling agent and the quality of the oil repelling film formed from the oil repelling agent. The solution called for using a coloring agent to facilitate visual examination.
Although the solution proposed by the publication may improve the visual examination of the quality of the oil repelling film, it has been found that the coloring agent in the proposed oil repelling agent generates a quantity of outgas that is markedly larger in volume than the outgas generated from other conventional oil repelling films. Outgas, for example, is generated by heat during operation of a hard disk drive, and by evaporation. This increase in the quantity of the outgas adversely effects the reliability of the hard disk drive. Also, the outgas may reduce the useful area of the magnetic disk and the density of the memory surface of the magnetic head. It is, therefore, desirable to produce a dynamic pressure device, such as a fluid dynamic pressure bearing device, with a reduced amount of generated outgas.
It is also desirable to produce such a dynamic pressure device without adding significant steps to conventional production processes, which are adapted for mass production.